The invention relates in general to an apparatus for rotating a screw-on connector onto the stripped ends of electric wires and thus securing them together.
Apparatus for attaching such screw-on connectors is known in the art, a typical unit being shown in U.S. Pat. No. 3,016,774, issued to M. M. Minobe on Jan. 16, 1962, which includes an elongated housing with an inlet for receiving the connectors and an outlet adjacent a turning station where the wires are twistably secured together and to the connector. A drive shaft positioned within the housing has a plurality of jaws secured to one of its ends, and the drive shaft is axially movable from a lower turning position, in which the jaws abut a cam surface to pivot inwardly and thereby grip the connector, to an upper position in which the connectors are released by the jaws. The cam surface is adjacent the outlet opening and is either fixedly or rotatably mounted to the elongated housing.
Such an apparatus has some disadvantages which make it relatively more expensive to operate and maintain. For example, in the Minobe U.S. Pat. No. 3,016,774 embodiment having a fixedly mounted cam surface the jaws contact the surface and are pivoted inwardly to grip a connector. As the jaws are being rotated about the end of a lower power shaft, they continuously slide against the cam surface and both the surface and the jaws are thereby subject to considerable wear. The Minobe patent embodiment having a rotatably mounted cam surface is subject to less wear, as the axially-movable lower shaft is lowered until the rotating jaws engage that surface to cause its rotation at substantially the same speed and to thereby reduce relative movement between the jaws and the cam surface. However, this arrangement requires the transmission of considerable torque by the lower power shaft so that the inertia of the cam surface and bearing about which it rotates may be overcome.
Furthermore in the said Minobe patent device, the lower and an upper shaft by which the lower shaft is driven are axially spaced apart and interengageable along a pair of cam surfaces which together effectively function as a slip clutch. The lower shaft on which the jaws are rotated is not directly driven by the upper shaft until the jaws grip the connector, at which point the jaws are in abutting engagement with the cam surface. Thus, the upper shaft must be rotating at a high, energy consuming speed before coming into direct driving contact with the lower shaft. This arrangement is further wasteful of energy in that the upper shaft, prior to direct driving engagement with the lower shaft, rotates without performing any useful work.